Jeep 1997 Grand Cherokee Service Manual page 1275

ZG
8W-39 VEHICLE THEFT SECURITY SYSTEM
DESCRIPTION AND OPERATION
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . 7
DESCRIPTION AND OPERATION
INTRODUCTION
The Body Control Module (BCM) operates the Vehicle
Theft Security System (VTSS). The BCM monitors the
vehicle doors, hood, liftglass in the liftgate, liftgate, and
ignition for unauthorized operation.
When the BCM detects unauthorized operation, it oper-
ates the horn repeatedly for three minutes and flashes the
headlamps and tail lamps for 15 minutes. Also, the engine
will not operate until the VTSS is disarmed.
The vehicle operator can activate the alarm by pushing
the panic button on the Remote Keyless Entry (RKE)
transmitter. When the operator pushes the panic button,
the radio frequency receiver in the Passenger Door Module
(PDM) receives the PANIC signal and broadcasts a mes-
sage on the CCD bus. When the BCM sees the PANIC mes-
sage on the CCD bus, it operates the horn repeatedly, turns
on the interior lights, and flashes the headlamps and tail
lamps. The BCM activates the panic alarm for three min-
utes unless the operator starts the vehicle and drives at a
speed above 15 MPH or pushes the panic button on the
RKE transmitter a second time.
When the ignition switch is in the START or RUN
position, it connects circuit A1 from fuse 8 in the
PDC to circuit A21. Circuit A21 powers circuit F99
through PDC fuse 18. Circuit F99 feeds the BCM.
In the ACCESSORY or RUN position, the ignition
switch connects circuit A1 to circuit A31. Circuit A31
powers circuit V23 through fuse 3 in the junction
block. Circuit V23 feeds the BCM.
VEHICLE THEFT SECURITY SYSTEM OPERATION
Each door, the liftgate, hood, and the liftglass in
the liftgate have an ajar switch that connects to the
Body Control Module (BCM). The ajar switches are
normally open when the doors, liftgate, liftglass and
hood are closed. When one of them open, its ajar
switch closes and connects the BCM to ground. In
response, if the Vehicle Theft Security System is
armed, the BCM starts the alarm. Refer to the Intro-
duction in this section for alarm information.
The BCM receives the ajar switch signals on the
following circuits.
• Circuit G75 provides the left front door ajar
switch signal
8W - 39 VEHICLE THEFT SECURITY SYSTEM
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INDEX
VEHICLE THEFT SECURITY SYSTEM
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 7
• Circuit G74 provides the right front door ajar
switch signal
• Circuit G77 provides the left rear door ajar
switch signal
• Circuit G76 provides the right rear door ajar
switch signal
• Circuit G78 provides the liftgate ajar and lift-
glass ajar signals
SYSTEM ARMING
The system alarm sets after the operator uses the power
door locks or Remote Keyless Entry (RKE) transmitter to
lock the doors and liftgate. After all doors and the liftgate
are locked and closed, the BCM illuminates a red Light
Emitting Diode (LED) (VTSS indicator light) on circuit
G69. The red LED is located on the top of the instrument
panel. The LED flashes rapidly signalling the system is
arming. It flashes at slower rate after approximately 15
seconds, indicating the BCM has set the VTSS.
SYSTEM DISARMING
The operator can disarm the system by unlocking a
front door or the liftgate with the key or the RKE
transmitter. The BCM monitors the lock cylinder
switch in each front door and the liftgate lock cylin-
der switches on circuit G71.
HORNS
When the BCM activates the horns, it energizes
the horn relay by providing a ground path for the
relay coil on circuit X4. Circuit F31 from fuse 6 in
the Power Distribution Center (PDC) powers the coil
and contact sides of the relay.
When the horn relay energize, its contact close and
connect circuit F31 to circuit X2. Circuit X2 feeds the
horns. Circuit Z1 provides ground for the horns.
PARKING LAMPS
The BCM operates the park lamps when it senses unau-
thorized entry to the vehicle while the Vehicle Theft Secu-
rity System is armed. When it senses unauthorized entry,
the BCM energizes the park lamp relay by providing
ground for the relay coil on circuit L79. Circuit 366 powers
the relay coil and contacts. When the relay energizes, it
connects circuit 366 to circuit L90. Circuit L90 powers the
park lamps, side marker lamps and tail lamps.
8W - 39 - 7
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